The broad objectives of the project are to describe and document the vascular and histologic details of the reparative processes of animal bone and joints as similar to human bone and joints as possible and to show clinical applications. The microcirculation and correlated histology of healing bone, under different conditions of repair, are being investigated against the background of the normal circulation in laboratory animals. Microangiography is the chief investigative tool in survival experiments of different durations, mainly on dogs. Standard histologic and tetracycline fluorophore observations are included. The results of osteotomy, fracture, internal fixation, bone grafting, implantation of foreign materials, and thermal necrosis of bone are being examined. Studies on the normal and reparative microcirculation and correlated histology of canine joints will be added to the project. Included will be experiments on degeneration and injury, on partial and complete replacemnt of articular surfaces, and on replacement of ligaments.